Integrally bonded, multilayer foamed product

ABSTRACT

By employing a unique manufacturing process, unique manufacturing equipment, or a unique combination of materials, a fully integrated, multilayer foamed thermoplastic or elastomeric member or profile having a core member peripherally surrounded by an outer protective layer is attained which is virtually incapable of being removed from said core member. By effectively melting the adjacent surfaces of the foamed layers being interengaged, a core member having any desired cross-sectional shape is produced and is peripherally surrounded with an outer layer integrally bonded thereto. In one aspect of the present invention, metallocene catalyzed plastic material is employed in forming the core member to impart desirable physical attributes thereto. In an alternate aspect of the present invention, a manufacturing method or processing equipment are employed for assuring the integral bonded engagement of the outer protective layer to the core member, on a mass produced basis, which assures secure, affixed, bonded interengagement of the protective layer to the core member.

TECHNICAL FIELD

This invention relates to foamed multilayer thermoplastic or elastomericmembers or profiles and, more particularly, to multilayer profileswherein an outer layer peripherally surrounds a core member in intimate,bonded interengagement therewith, as well as methods and equipment usedfor manufacturing said members or profiles.

BACKGROUND ART

For over four decades, extruded thermoplastic or elastomeric foamarticles have been manufactured and distributed for a wide variety ofuses. Over the years, numerous additional end products have benefittedfrom foamed thermoplastic or elastomeric members. Typical applicationsand fields in which such products have received substantial use anddistribution include toys, furniture, beddings, packaging, shockabsorption, construction, agriculture, insulation, and recreation.

In developing additional markets for foamed thermoplastic andelastomeric members, the practice of reducing the density of the polymerresin to produce a foamed article having a low density has receivedincreasing attention. Presently, thermoplastic or elastomeric foams arecategorized as either high or low density foam and are divided atapproximately 240 kg/m³ (15 lbs/ft³).

Many favorable advantages are attained by reducing the density of thefoamed products. Typically, these favorable properties include anincrease in insulation value, an increase in flexibility of the product,cost reduction, higher resiliency, and increased rates of production.Unfortunately, some desirable properties are sacrificed with densityreduction, such as a reduction in mechanical properties of the resultingproduct. Typically, mechanical properties are reduced at an approximaterate proportional to one over the density reduction squared. In order toovercome the reduction in mechanical properties, many applicationsemploy a combination of different materials having different densities,attempting to produce a resulting product which will possess the desiredphysical characteristics.

Typically, thermoplastic or elastomeric members of this nature whichincorporate a plurality of different materials of different densitiesare produced by coextrusion or cross-head extrusion. By employing eitherof these processes, two or more distinct layers are combined in asingle, or multi-step extrusion operation to produce a final producthaving separate and distinct layers of varying material compositionsand/or material densities. These distinct layers may or may no possessintegrally bonded interfaces.

The principal distinction between co-extrusion and cross-head extrusionis the number of operations required to produce the final product. In acoextrusion process, a single operation is employed wherein differentpolymer melts or resins having vastly different properties are combinedin a single production operation. In a cross-head extrusion process, onelayer of the material is formed and thereafter, the additional layer orlayers are applied in a subsequent extrusion operation.

Regardless of which process is employed, the resulting product comprisesa plurality of layers integrally bonded to each other with each layerbeing formed from materials having either a different composition and/ora different density. In addition, other properties such as aesthetics,gas or vapor permeability, organoleptic barriers, printability,sealability, and the like constitute properties often imparted to one ormore of the layers in order to provide a final product having particularcharacteristics.

In most applications, it has been found that cross-head extrusion ishighly advantageous when vastly different types of material are to becombined together. Some applications benefitting from a cross-headextrusion process are for products such as plastic coated wires,protective or insulating coatings over metal or rigid materials. Inaddition, a foam layer peripherally surrounding a solid object or asolid layer peripherally surrounding a foam core are further examplesbenefitting from being produced by cross-head extrusion. In addition,the application of a more expensive or highly specific coating or layer,such as an antimicrobial layer or a corrosion resistent layer over aless expensive supporting substrate are further examples benefittingfrom cross-head extrusion processes.

Another area in which integrally bonded, multi-layer thermoplastic orelastomeric members have been extensively employed is for improvingproduct safety in general and reducing injury to individuals due tounwanted or unexpected contact with the underlying product. In thisregard, metal frames of products in support structures used by children,the elderly, the injured, or infirm individuals have receivedsubstantial attention and have been manufactured and/or improved byemploying padding or cushioning protection in order to reduce oreliminate injuries that could result from contact.

Examples of such products are found in amusement parks and playgroundsand include slides, swing sets, moving vehicles, etc. In order toeliminate or reduce injuries, these products are now either manufacturedwith or retrofitted with padding or thermoplastic or elastomeric foammaterial to provide a soft, cushioned outer surface to otherwise hardsurfaces or structures. In addition to the products detailed above,numerous other products such as race cars, baby furniture, bicycles,hospital beds, support posts for basketball, volleyball, and the like,gym equipment, boat fenders, etc. have all been manufactured withpadding or thermoplastic or elastomeric foam constructions for addedprotection.

In addition, numerous products are manufactured with padded or cushionedouter surfaces for decorative purposes. These products include showbooth displays, window displays, and the like. Furthermore, foamencapsulated products have also been commonly employed for insulatingpurposes, in order to conserve energy and reduce unwanted heat lossthrough various sources, such as hot water pipes which are exposed tosubstantially lower ambient temperatures.

In attempting to meet the demands for the products detailed above,foamed thermoplastic and/or elastomeric materials, such as polyethylene,have been accepted as the principal materials for meeting most productrequirements. This acceptance has been caused by the ability of foamedthermoplastic and elastomeric to be formed in numerous sizes, shapes,and configurations. As a result, virtually any product can beeffectively and efficiently improved by having the surface thereofcovered by a soft, insulating, or cushioning member.

Although the products to be enhanced by incorporating an outer cushionedsurface comprise a wide variety of sizes and shapes, elongated,cylindrically-shaped tubes typify the principal market for cushionedsurfaces. Since elongated cylindrical tubes are used to manufactureposts, slides, railings, water pipes, swing sets, etc., it is readilyapparent that such tube members form the principal market area whereincushioning is desired.

As a result, elongated, longitudinally extending thermoplastic orelastomeric tubes formed from polyethylene foam material have beenwidely accepted and employed on numerous products for providing thedesired soft, compressible, injury reducing surface thereto.Unfortunately, it has been found that these products have been unable tomeet all of the demands imposed thereon.

One particular significant drawback that has occurred in these prior artuses, which has been incapable of being satisfactorily resolved, is theinability of these prior art elongated, thermoplastic or elastomerictubes to withstand repeated abrasion, use, or contact. In general,although these prior art products do provide the desired soft,cushioning surface being sought, these prior art products arecontinuously receiving repeated contacting use in their installedposition, and quickly degrade due to such use.

Prior art foam tubes are typically employed peripherally surrounding andprotecting the hard outer surface of playground equipment found inretail outlets, such as food chains, as well as in swing sets employedat home. In order to protect the children playing on this equipment, thesupporting frames and exposed metal surfaces are protected withthermoplastic or elastomeric cushioning means. However, during normalplay, the children use this equipment continuously, kicking, rubbing,cutting, pulling, and tearing at the thermoplastic foam surfaces,causing such surfaces to be quickly degraded.

Another problem encountered in prior art installations is the inabilityof the thermoplastic or elastomeric components to withstand exposurefrom dirt, ink pens, and the like as well as exposure to pencils,crayons, and the like. As a result, in a relatively short time period,newly installed thermoplastic or elastomeric foam members becomevisually unappealing and unattractive.

In order to overcome these drawbacks, some prior art systems haveattempted to peripherally envelope the thermoplastic or elastomeric foamtubes or members with a self-locking or self-sealing protective layer orsheet. Although the installation of such protecting sheets or layershave extended the life of the underlying thermoplastic or elastomerictubes or members, the protecting sheets or layers are typicallyseparated from the substrate they are protecting by the activities ofthe users and stripped from their surrounding position. As a result, thesurfaces of the underlying thermoplastic or elastomeric members arequickly exposed to physical contact and surface degradation.

Therefore, it is a principal object of the present invention to providea foamed, multi-layered, thermoplastic or elastomeric member/profilewherein the layers are integrally bonded to each other, providing amulti-layered product having precisely desired physical characteristics.

Another object of the present invention is to provide a foamed,multilayered thermoplastic or elastomeric member/profile having thecharacteristic features described above which is capable of beingquickly and easily mounted to any desired product to provide the desiredphysical attributes thereto.

Another object of the present invention is to provide a foamed,multilayered thermoplastic or elastomeric member/profile having thecharacteristic features described which is producible in an elongatedtubular or cylindrical form and is capable of being easily and quicklyinstalled on any desired curved surfaced to provide a soft, cushioningprotection thereto, while also eliminating product degradation or colordiscoloration during use.

Another object of the present invention is to provide a foamed,multilayered thermoplastic or elastomeric member/profile having thecharacteristic features described wherein the outer layer is inherentlyscratch and puncture resistent, while also being capable of being easilycleaned to provide product longevity and long lasting visual appeal.

A further object of the present invention is to provide a foamed,multilayered thermoplastic or elastomeric member/profile having thecharacteristic features described which is capable of being produced invirtually any desired color, configuration, surface treatment, andphysical characteristics.

Another object of the present invention is to provide a foamed,multilayered thermoplastic or elastomeric member/profile having thecharacteristic features described wherein each of the layers areintegrally bonded to the adjacent layer, preventing unwanted removal orpeeling of the layers from each other.

Another object of the present invention is to provide a foamed,multilayered thermoplastic or elastomeric member/profile having thecharacteristic features described which incorporates layers that arewater impermeable while also providing substantially increasedresistance to degradation by contact with chemicals.

Another object of the present invention is to provide a foamed,multilayered thermoplastic or elastomeric member/profile which iscapable of being mass produced in any desired quantities, therebyproviding a competitively priced product.

Other and more specific objects will in part be obvious and will in partappear hereinafter.

SUMMARY OF THE INVENTION

By employing the present invention, all of the difficulties anddrawbacks found in the prior art have been eliminated and a fullyintegrated, multi-layer foamed thermoplastic or elastomericmember/profile is attained. In accordance with the present invention,this achievement is reached by employing a unique combination ofmaterials for the layers being integrally bonded to each other as wellas by employing a unique process for manufacturing the resultingproduct. In this way, a final product is realized which completelyovercomes the problems found in prior art systems and provides a unique,highly desirable and competitively produced long lasting product.

By employing the present invention, any desired configuration ofcross-sectional shape of an integrally bonded, multi-layered, foamedthermoplastic or elastomeric member/profile can be produced. Forexemplary purposes only, the disclosure provided herein focuses onsubstantially circular shaped cross-sectional members, due to theirbroad applicability and use in a wide variety of product areas. However,although foamed thermoplastic or elastomeric members/profiles having asubstantially circular cross-sectional shape are detailed herein, thepresent invention is intended to encompass all products, regardless ofthe cross-sectional shape or form of the member or profile.

In the present invention, an integrally bonded, multi-layered, foamedthermoplastic or elastomeric member/profile comprises a core memberformed from extruded, foamed plastic polymers, copolymers, orhomopolymers. Although any known foamable plastic material can beemployed in the extrusion process for developing the thermoplastic orelastomeric member/profile of this invention, with the foamable plasticmaterial comprising either open cell or closed cells, the particularplastic material employed is selected to produce the desired physicalattributes being sought for the particular characteristics of the endproduct. However, in general, the density of the foam core preferablyranges between about 10 and 500 kg/m³.

Most foamed thermoplastic or elastomeric materials are categorized aseither high density or low density. Typically, 240 kg/m³ represents thedividing line wherein these materials are classified. As detailed below,although high density foam materials can be employed and benefit fromthe present invention, the detailed disclosure focuses on low densityflexible foams since such products have greater commercial interests innumerous applications. In fact, in the preferred embodiment of thepresent invention, the foamed thermoplastic or elastomeric core membercomprises a density ranging between about 10 kg/m³ and 100 kg/m³.However, although most products produced in accordance with the presentinvention, as detailed herein, comprise this density range, otherproducts having density ranges between about 10 kg/m³ and 500 kg/m³ canbenefit from the teaching of the present invention and are all intendedto be within the scope of the present invention.

One of the principal aspects of the present invention is the preferableincorporation of metallocene catalyzed polyethylenes in the formulationof the foam material employed for the core member. In this regard, themetallocene catalyzed polyethylene material can range between about 5%to 95% by weight of the entire weight of the core member or profile. Byemploying metallocene catalyzed polyethylene material in the formulationof the plastic material employed for forming the core member,substantially desirable physical characteristics are realized.

By employing metallocene catalyzed polyethylenes as one ingredient ofthe plastic materials forming the core member, a substantially improvedintegral bond is realized between the low density inner core foam layersand the higher density outer layer integrally bonded therewith. Inaddition, physical properties such as tensile strength and tear strengthare also substantially improved, along with the elongation forcerequired to break the material. As a result of these substantiallyimproved physical characteristics, along with other attributes detailedherein, the core member of the present invention incorporatesmetallocene catalyzed polyethylene material as at least one ingredientthereof.

In addition to the metallocene catalyzed polyethylene material, otherplastic materials are employed. Preferably, the other plastic materialsare selected from the group consisting of inert polymers, homopolymers,monomers, and copolymers. By employing these materials, in combinationwith the metallocene catalyzed polyethylene, the desirable physicalcharacteristics for the resulting core member are realized.

In order to further enhance the properties of the foam thermoplastic orelastomeric core member, any desired additives can be incorporated intothe polymer material forming the core member. In this regard, additivesselected from the group consisting of color, flame retardants,ultraviolet stabilizers, blowing agents, and other additives known tothose skilled in this art can be employed to provide the desired endproduct characteristics. In this way, the final properties sought by aparticular end user can be attained.

By employing the present invention, an outer, peripherally surroundingprotective layer is integrally bonded to the core member in a mannerwhich virtually eliminates all of the prior art difficulties encounteredwith removal, separation, or dislocation of the outer protective surfacefrom the base material. In order to provide an outer protective surface,the peripherally surrounding, outer layer preferably comprises a densitygreater than the density of the core material, with the outer layerbeing formed from material which provides inherent rigidity andstrength, as well as resistance to degradation, puncturing, surfaceabrasions, etc. In this regard, an outer layer having an overall densityranging between about 100 kg/m³ and 1200 kg/m³ has been found to provideoptimum results.

In addition to employing a material formulation constructed forimparting the desired physical characteristics to the outer,peripherally surrounding layer, additives may also be incorporated intothe material when applied to the core material. Such additives wouldtypically include density reducing agents, chemical blowing agents,pigments, flame retardants, ultraviolet stabilizers, talc, fibers,fillers, stiffness enhancers, as well as other known additives commonlyemployed in this art.

By employing the present invention, a foamed thermoplastic orelastomeric core member is peripherally surrounded by an outer surfaceforming, protective layer which is integrally bonded directly to theouter surface of the thermoplastic or elastomeric core member. In thisway, the outer protective layer forms the exposed surface of theresulting thermoplastic or elastomeric member/profile, providing aprotective outer surface which is capable of withstanding abrasion,grease, ink, dirt, chemical, physical and environmental contamination,discoloration, and vandalism. As a result, a fully integratedstructurally beneficial, multilayer, foamed thermoplastic or elastomericmember/profile is realized which is capable of providing a soft,cushioning protection to any desired surface, while also virtuallyeliminating unwanted and undesirable damage to the multilayer foamedthermoplastic or elastomeric member.

In addition to providing a unique product formulation for attaining theintegrally bonded multilayer foamed thermoplastic or elastomericmember/profile of the present invention, a unique method ofmanufacturing this product is also attained. In the present invention,an easily executed, inexpensive, efficient process is provided whereinthe integrally bonded, multilayer foamed thermoplastic or elastomericmember/profile of the present invention is attained on a mass producedbasis, using extrusion foam equipment. By employing the process of thepresent invention, a low density foamed thermoplastic or elastomericcore member is peripherally surrounded and fully encapsulated with anextruded, high density polymer layer thoroughly bonded to the coremember in a manner which provides integral, bonded interengagementbetween the components in an efficient, controlled manner.

In the process of the present invention, the foamed thermoplastic orelastomeric core or substrate is formed using conventional foamextrusion methods. Once this material has been formed, it may be storedfor any desired time period until application of the outer layer isdesired. Then, using a uniquely constructed cross head die, thepreformed substrate is passed through the cross head die, securelyaffixing the outer, peripherally surrounding, encapsulated protectivelayer to the substrate.

In applying the peripherally surrounding protective layer to the corematerial employing the process of the present invention, the plasticmaterial being employed for the protective layer is prepared in aconventional manner and passed through the cross head die with thetemperature thereof being precisely maintained by the cooperatinglyassociated heating chambers peripherally surrounding and fullyenveloping the entire polymer flow zones within the cross head die.

In the preferred construction, the heating chambers are constructed toassure that the heating means passing through the chambers traverses allof the polymer flow equally throughout all passageways thereof. In thisway, the precisely desired temperature level for the polymer flow ismaintained. In addition, in the preferred construction, the outersurface of the die is surrounded by heating means in order to assurethat the precisely desired temperature levels are maintained throughoutall areas of the cross head extrusion die.

Another feature incorporated into the cross head die system of thepresent invention is the delivery angle at which the encapsulated,peripherally surrounding polymer melt is delivered to the substrate forapplication to the surface of the substrate. In this regard, it has beenfound that the approach angle is important in assuring that the polymermelt being applied to the substrate surface will exert sufficientpressure on the substrate to achieve the desired homogeneous, integralbonding therewith, while not exerting excessive forces thereon. Ingeneral, a delivery angle ranging between about 30° and 90° ispreferred.

In the preferred construction, the cross head die of the presentinvention incorporates a substrate densification zone wherein thesubstrate material is transferred in a manner which ruptures the closedcells near the substrate surface, effectively increasing the density inthis area. Typically, either air or the blowing agent employed informing the substrate is retained in the closed cells of the substrate.Consequently, by rupturing these cells, the blowing agent is released.If the blowing agent is not released from the surface cells, the cellsmay be broken later, producing pockets of the blowing agent between thesubstrate and the outer layer. If this occurs, the intimate bondedinterengagement between these two layers is reduced.

In order to aid in the release of the trapped gas(es) from the cells ofthe outer surface of the substrate, the substrate is heated as thesubstrate is passed through the cross head die of the present invention.By passing the substrate through a predefined length of the cross headdie wherein the substrate is preheated, the gas(es) retained within thecells of the outermost layer of the substrate is released. In addition,vacuum means are provided in the cross head die to remove the blowingagent as the trapped gas(es) are released from the uppermost layer ofcells of the substrate material. In this way, any retention of thegas(es) between the two layers is eliminated.

In addition, in the preferred construction, the heated zone is ramped orsloping in order to compress or squeeze the substrate simultaneouslywith the heating thereof. In this way, substantially increased numbersof cells are broken and gas removal is optimized. As a result, thesurface of the substrate is enhanced for providing the desired integral,bonded, engagement of the protective layer to the substrate.

The invention accordingly comprises the several steps and the relationof one or more such steps with respect to the other, the apparatusembodying the features of construction, combination and arrangement ofparts which are adapted to effect such steps, and the article producedwhich possesses the characteristics, properties, and relation ofelements all as exemplified in the detailed disclosure hereinafter setforth with the scope of the invention being indicated in the claims.

THE DRAWINGS

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings, in which:

FIG. 1 is a perspective view of one embodiment of an elongated,multilayer, integrally bonded foamed thermoplastic or elastomericmember/profile manufactured in an elongated, hollow, cylindrical shapein accordance with the present invention;

FIG. 2 is a cross-sectional top plan view of a cross head dieconstructed for being employed using the process of the presentinvention; and

FIG. 3 is an enlarged cross-sectional view of the encircled area of FIG.2.

DETAILED DESCRIPTION

By employing the present invention, integrally bonded, multilayered,foamed thermoplastic or elastomeric members or profiles are formedincorporating any desired cross-sectional shape or configuration, witheach of the profiles possessing an outer layer peripherally surroundingand enveloping the core member and providing the core member with aprotective outer surface which resists all types of degradation as wellas chemical and physical attacks. Although the present invention can beemployed with a foam core having virtually any desired configuration,size, or shape, the present invention is detailed herein in relationshipto an elongated, substantially cylindrically shaped, hollow foamed coremember, peripherally surrounded and enveloped by an integrally bondedprotective layer. However, it is to be understood that the embodimentdepicted and detailed in this disclosure is for exemplary purposes onlyand is not intended to limit the scope of the present invention.

As shown in FIG. 1, elongated, substantially cylindrically shaped,integrally bonded, multilayer member or profile 20 comprisesthermoplastic or elastomeric foamed substrate or core member 21 andouter layer 22 peripherally surrounding the surface of core member 21.As detailed herein, outer, peripherally surrounding layer 22 is insecure, bonded, affixed interengagement with core member 21.Furthermore, as depicted in FIG. 1, elongated, cylindrically shapedfoamed thermoplastic or elastomeric core member 21 incorporates acentral hollow zone 24.

Preferably, integrally bonded, multilayer member/profile 20 alsoincorporates a longitudinally extending slit 23 which extends from outerlayer 22 through the entire thickness of thermoplastic foam core member21, forming an entryway into the longitudinally extending hollow centralzone 24 of thermoplastic or elastomeric core member 21. Although neithercentral hollow zone 24 nor longitudinally extending slit 23 representmandatory components of this construction, these features are depictedand discussed herein, since they represent the most common form for anelongated, cylindrically shaped member of this nature.

By achieving integrally bonded, multilayer, foamed member/profile 20 ofthe present invention with outer layer 22 peripherally surrounding andfully enveloping foamed thermoplastic or elastomeric core member 21,while also being securely affixed in intimate, bonded interengagementtherewith, a product is achieved which is capable of overcoming all ofthe prior art drawbacks and difficulties. By establishing integrallybonded, multilayer foamed member/profile 20, as depicted in FIG. 1,member/profile 20 is easily mounted in any desired location for anydesired application, such as swing sets, gym equipment, play yardequipment, etc. peripherally surrounding and protecting the hard surfacecomponents thereof. By employing integrally bonded, multilayer foamedmember/profile 20, the particular hard surface components are coveredwith a soft cushioning layer, while also possessing outer layer 22 whichis capable of withstanding exposure to environmental degradation as wellas chemical and physical attacks attempting to erode, puncture, orremove outer layer 22 from core member 21.

In addition, outer layer 22 also imparts abrasion resistance tointegrally bonded, multilayer foamed member/profile 20, enablingmember/profile 20 to withstand repeated abrasion, abutting, and evenpuncturing contact, without incurring degradation of outer layer 22, aswell as access or degradation of core member 21. As a result, thepresent invention is capable of virtually eliminating all of thedrawbacks and difficulties found with prior art systems.

In the preferred embodiment, elongated, cylindrically shaped, foamedthermoplastic or elastomeric core member 21 is formed from athermoplastic polymer, elastomeric polymer, copolymer, homopolymer ormixture thereof. On general, it has been found that such products arepreferably formed from polyethylene and are constructed with the finalpolyethylene foam having a density ranging between about 10 kg/m³ and500 kg/m³. If desired, any natural or synthetic rubber or mixtures ofnatural or synthetic rubber with thermoplastic polymers can also beemployed with equal efficacy, with departing from the scope of thepresent invention.

In forming elongated, foamed thermoplastic or elastomeric core member21, the desired composition is mixed and then chemically or physicallyblown, using a conventional extrusion process, forming the desired shapein the precisely desired size and configuration. In achieving thisresult, the cells can be either open or closed cells, with the coremember being formed in any desired hardness or softness. Furthermore,although FIG. 1 depicts thermoplastic or elastomeric core member 21formed as an elongated, hollow tube member, core member 21 may compriseany desired size and shape as well as being formed with or without ahollow zone.

Although any desired thermoplastic polymer, elastomeric polymer,copolymer, homopolymer, or mixtures thereof may be employed to formthermoplastic or elastomeric core member 21, the preferred plasticmaterial is preferably selected from the group consisting ofpolyethylenes, metallocene catalyzed polyethylenes, polybutylenes,polyurethanes, silicones, vinyl based resins, thermoplastic elastomer,polyesters, ethylene acrylic copolymers, ethylene-vinyl-acetatecopolymers, ethylene-methyl acrylate copolymers, ethylene-butyl-acrylatecopolymers, ethylene-propylene-rubber, styrene butadiene rubber,ethylene-ethyl-acrylic copolymers, ionomers, polypropylenes, andcopolymers of polypropylene and copolymerizable ethylenicallyunsaturated commoners. Furthermore, in those instances when polyethyleneis employed, it has been found that the polyethylene may comprise one ormore polyethylenes selected from the group consisting of high density,medium density, low density, linear low density, ultra high density, andmedium low density.

The particular material employed for core member 21 is selected basedupon the end use for which the multilayer foamed member/profile 20 is tobe employed. In this regard, for use as a cushioning member on metallicor other rigid or hard surfaces, it has been found that a density below240 kg/m³ is employed, so as to provide a core member which isclassified as a low density flexible foam member. In addition, it hasbeen found that a density ranging between about 10 kg/m³ and 100 kg/m³is preferred. By employing a foam core member of this nature, thedesired soft cushioning, compressibility, and shock mitigation isattained, while also providing resiliency for returning to its originalconfiguration after impact.

In order to provide the desired resistance to chemical and physicaldegradation, the principal characteristics from which prior art productshave suffered, a foamed thermoplastic or elastomeric core member 21 ofthe present invention is preferably formed incorporating between about5% and 95% metallocene catalyzed polyethylene as one of the componentsthereof. As detailed herein, by employing metallocene catalyzedpolyethylenes as one of the materials selected for the composition ofthe thermoplastic or elastomeric core member 21, increased resistance totearing as well as increased bonding strength is realized. Furthermore,it has been found that in the preferred composition, the metallocenecatalyzed polyethylenes ranges between about 20% to 60% by weight of theentire weight of the composition of the thermoplastic or elastomericcore member.

In the preferred construction, the foamed thermoplastic or elastomericcore member is formed with a density ranging between about 10 kg/m³ and100 kg/m³. Furthermore, in most applications wherein a low densityfoamed member is desired, densities ranging between about 16 kg/m³ and60 kg/m³ are preferred. In addition to this density range, the resultingfoamed thermoplastic or elastomeric core member 21 also comprises a cellsize ranging between about 0.5 mm and 10 mm. Although foams having acell size falling within this range have been found to be well suitedfor providing the desired physical and chemical characteristics, thecell size of the resulting thermoplastic or elastomeric core member 21preferably ranges between about 2.0 mm and 6.0 mm.

In addition to incorporating a metallocene catalyzed polyethylene in theplastic material forming foamed thermoplastic or elastomeric core member21, any other desired additives may also be employed for attainingspecific physical characteristics. Although any desired additive can beemployed, typical additives used in the plastic material are selectedfrom the group consisting of flame retardants, ultraviolet stabilizers,nucleating agents, physical and chemical blowing agents, volumestabilizing agents, colorants, and pigments.

As discussed above, by employing metallocene catalyzed polyethylenes asa component of the plastic material employed for forming foamedthermoplastic or elastomeric core member 21, substantially improvedphysical properties are attained. These physical properties includetensile strength, tear strength, elongation to break, as well as bondingor sealing strength. In order to demonstrate the efficacy ofincorporating metallocene based polyethylenes in the formulation of thefoamed thermoplastic or elastomeric core member 21, several samples wereprepared employing different quantities of metallocene catalyzed lowdensity polyethylenes in combination with low density polyethylene.After preparation, each sample was tested to determine the tearstrength, tensile strength and elongation to break. In addition, afoamed thermoplastic or elastomeric member was formed using only lowdensity polyethylene, with the same tests being performed thereon forcomparative purposes. By referring to Table I, the results attained fromthese tests are provided.

                  TABLE I    ______________________________________                         10%     20%   30%   40%    Property Material                 LDPE    mLDPE   mLDPE mLDPE mLDPE    ______________________________________    Tear Strength lbs/in.                 3.1     5.1     6.23  10.2  11.7    Tensile Strength lbs/in.sub.2                 39.0    36.8    39.0  43.5  46.7    Elongation to Break %                 57.8    68.9    79.2  115.8 152.3    ______________________________________     Density of each sample = 32 kg/m.sup.3     Cell size of each sample = 1.0 mm

As is evident from a review of Table I, by increasing the amount ofmetallocene catalyzed polyethylene employed in the plastic materialforming the foamed thermoplastic or elastomeric core member, the tearstrength, tensile strength, and elongation to break of the resultingfoam member are increased. When 20% and less of a metallocene catalyzedpolyethylene is employed, the resulting product has a tensile strengthsubstantially equal to, or slightly less than, the tensile strength of afoamed core member formed entirely from low density polyethylene.However, by increasing the quantity of metallocene catalyzedpolyethylene above 20% by weight of the weight of the entire plasticmaterial, the tensile strength attained is substantially greater thanthe tensile strength provided by a foamed core member manufacturedentirely from low density polyethylene. As noted in Table I, in eachinstance, the foamed core member comprises a density of 32 kg/m³ (2pounds per foot cubed) with a cell size maintained at about 1.0 mm.

As also shown in Table I, the tear strength property of the foamedthermoplastic or elastomeric member incorporating 10% metallocene wasincreased by over 66% when compared to the foam member comprising 100%low density polyethylene. Furthermore, by incorporating greaterquantities of metallocene catalyzed polyethylene in the composition, thetear strength property was additionally increased in each sample.

Table I also clearly demonstrates that the inclusion of metallocenecatalyzed polyethylene caused the percent elongation to break to beincreased and that each time more metallocene catalyzed polyethylene wasemployed, a high elongation to break was obtained. As is evident fromthese results, substantially superior physical characteristics areproduced by combining metallocene catalyzed polyethylene as one of thecomponents of the plastic material employed for forming the foamedmember. These physical characteristics, as well as additional physicalcharacteristics detailed herein, provide a foam member which enables anouter layer to be securely bonded thereto, overcoming all of the priorart difficulties and producing the unique construction of the presentinvention.

In order to provide the desired peripherally surrounding, protective,intimate, bonded interengagement of outer layer 22 with foamedthermoplastic or elastomeric core member 21, outer layer 22 ispreferably formed from plastic material substantially identical orsimilar to the plastic material employed for core member 21. However, asdetailed herein, the physical characteristics imparted to outer layer 22differ substantially from the physical characteristics of core member21.

In the preferred construction, outer layer 22 is constructed toperipherally surround and fully envelop thermoplastic or elastomericcore member 21 while being intimately bonded thereto, with thecontacting surfaces thereof being intimately interengaged with eachother. Furthermore, in order to provide the protective characteristicsdesired for outer layer 22, outer layer 22 comprises a thickness rangingbetween about 0.1 mm and 5 mm. However, depending on the productdesired, outer layer 22 may be formed with any thickness, either in asingle application or in multiple applications.

In order to achieve an outer layer 22 which is resistant to thephysical, chemical, and environmental abuses required for achieving thegoals of the present invention, outer layer 22 preferably comprises adensity ranging between about 100 kg/m³ and 1,200 kg/m³. Although thisrange has been found to produce an outer layer which is highly effectivein possessing all of the desired physical characteristics, it has beenfound that the density of outer layer 22 preferably ranges between about500 kg/m³ and 1,200 kg/m³.

In order to provide outer layer 22 which is in intimate bondedinterengagement with core member 21, it is important that the plasticmaterial employed for outer layer 22 be compatible with the plasticmaterial employed for core member 21. In this regard, plastic materialeither identical, compatible, or similar to the plastic materialemployed for core member 21 is employed. In the preferred embodiment,outer layer 21 is formed from plastic material selected from the groupconsisting of metallocene based low density polyethylenes, low densitypolyethylenes, ethylenic copolymers, ethylene-vinyl-acetates,ethylene-butyl-acrylates, ethylene-methyl acrylate, ethylene acrylicacid, di-block and tri-block ethylene styrene, and ethylene butylenestyrene copolymers.

In addition to the plastic materials forming the composition of outerlayer 22, other additives normally employed in foaming thermoplastic orelastomeric materials may be employed. Although any desired additivescan be used without departing from the scope of this invention,preferred additives employed in the formulation are selected from thegroup consisting of density reducing agents, physical or chemicalblowing agents, pigments, flame retardants, ultraviolet stabilizers,talc, fibers, and fillers.

In order to achieve the desired integral bonded interengagement betweenouter layer 22 and core member 21, outer layer 22 is formed about coremember 21 using a process which provides the desired secure, affixed,interengagement of outer layer 22 to the outer surface of core member 21in substantially its entirety. As detailed below, this intimate bondedinterengagement is preferably attained by employing a cross headextrusion process.

Although cross head extrusion is known in the art and has been employedfor many years, the unique equipment and process steps detailed hereinprovide a construction which attains a novel manufacturing process whichenables outer layer 22 to be intimately bonded in secure affixation tocore member 21 in a mass producible, continuous manufactured extrusionsystem. By employing the process and extrusion dies detailed below,outer layer 22 is applied to core member 21 peripherally surroundingcore member 21 in its entirety and fully encapsulating core member 21with outer layer 22 in a secure, bonded, interengagement therewith,producing an outer protective layer for core member 21 which resistsenvironmental, chemical, and physical abuse and/or degradation. As aresult, the desired integrally bonded, multilayer foamed member/profile20 of the present invention is attained.

Furthermore, by employing any desired additives in the formation ofouter layer 22, as detailed above, member/profile 20 is attained with anouter surface which is chemically resistant to unwanted attacks,electrostatically dissipative, heat resistant, flame retardant,ultraviolet stabilized, and incorporates any desired visual colorings,additives, or effects.

By referring to FIG. 2, along with the following detailed disclosure,the application of outer layer 22 to core member 21 using the process ofthe present invention can best be understood. In order to attain asecure, bonded, affixed interengagement of outer layer 22 with coremember 21, a cross head extrusion die system is employed. As a result,foamed thermoplastic or elastomeric core member 21 is formed in aconventional extrusion process and stored until ready for application ofouter layer 22 thereto. When the peripheral surrounding bondedinterengagement of outer layer 22 to core member 21 is desired, auniquely constructed, cross head extrusion die 30 of the presentinvention is employed.

As shown in FIG. 2, cross head extrusion die 30 of the present inventionis constructed for peripherally surrounding and fully enveloping theparticular shape of foamed thermoplastic or elastomeric core member 21.As depicted in FIG. 2, with core member 21 comprising a hollowcylindrical shape, cross head extrusion die 30 is constructed with anelongated, cylindrical passageway 31 which is dimensioned forcooperating with the configuration of core member 21.

Passageway 31 comprises an entry portal 32 and an exit portal 33. Asfurther detailed below, elongated passageway 31 is formed in threeseparate and distinct zones or sections, larger diameter section 34,central section 35, and smaller diameter section 36. Section 34comprises a first, larger diameter zone which is dimensioned forreceiving cylindrically shaped, elongated, formed thermoplastic orelastomeric core member 21 as originally produced, in a manner whichwill enable core member 21 to contact section 32, while also beingslidably engageable therewith. Central section 35 of passageway 31comprises a sloping, tapering section which compresses and densifiescore member 21, as part of the manufacturing process. Finally, smallerdiameter section 34 of passageway 31 is generally circular incross-section, having a diameter consistent with the diameter desiredfor the final integrally bonded, multilayer foamed member/profile of thepresent invention.

In the preferred embodiment of the present invention, cross head die 30comprises two principal portions, a die body portion 40 and a vacuumbody portion 41. Vacuum body portion 41 incorporates entry portal 32 andlarger diameter section 34 of passageway 31. In addition, vacuum bodyportion 41 incorporates a vacuum channel 42, which extends throughvacuum body portion 41 terminating exteriorly with exit portal 43, andterminating interiorly with portal 44.

In the preferred embodiment, exit portal 43 of vacuum channel 42 isconnected directly to a vacuum source which maintains vacuum conditionsthroughout channel 42. In addition, interior portal 44 is interconnectedwith an annual interior cavity 45 which is continuously maintained undervacuum conditions due to the construction and operation of vacuumchannel 42. In addition, annual interior cavity 45 establishes atransition between large diameter section 34 and central, ramped,sloping section 35 of passageway 31. As is more fully detailed below,this transition, as well as the establishment of an annular interiorcavity 45, which is maintained continuously under vacuum conditions,assures the removal of unwanted gases.

Die body portion 40 of cross head die 30 of the present inventionincorporates a polymer melt delivery channel 50 which extends from exitportal 51 formed at the outer surface of cross head die 30 to aninterior portal 52 formed in cooperative association with smallerdiameter section 36 of passageway 31. In the preferred embodiment,polymer melt delivery channel 50 comprises a holding zone 53 formedbelow exit portal 51 internally within die body portion 40 andinterconnected to exit portal 51 with an enlarged interconnectingpassageway. In addition, polymer melt delivery channel 50 also comprisestwo cooperating, reduced diameter polymer melt feed lines formed aspolymer melt delivery feed line 54 and polymer melt metering feed line55. In particular, as detailed below, the angular relationship ofpolymer melt metering feed line 55 to smaller diameter section 36 ispreferably controlled in a precisely desired relationship, in order toproduce secure, affixed, bonded interengagement of outer layer 22 tocore member 21.

Die body portion 40 of cross head extrusion die 30 also incorporates aplurality of cavities formed therein within which heating means arepositioned in order to provide precisely desired temperature levelswithin die body portion 40. In this regard, die body portion 40incorporates cavities 58 and 59 near the exterior surface of die bodyportion 40 directly adjacent exit portal 41, holding zone 53, and theinterconnecting passageway therebetween. By employing suitable heatproducing means within cavities 58 and 59, the polymer melt beingemployed for producing outer layer 22 is maintained at the preciselydesired temperature level to assure that the polymer melt will flowthrough die body portion 40 in the precisely desired manner.

In addition, die body portion 40 also comprises a cavity 60 directlyadjacent polymer melt delivery feed line 54 and polymer melt meteringfeed line 55 in order to maintain the polymer melt passing therethroughat the precisely desired temperature. Finally, die body portion 40 alsocomprises an annular cavity 61, formed directly adjacent sloping,tapered, intermediate section 35 of passageway 31 to raise thetemperature level of the outer surface of core member 21 as detailedbelow.

In each of the cavities detailed above, namely cavities 58, 59, 60, and61, each cavity is substantially annular in configuration, formedthroughout the entire die body portion 40. In this way, the preciselydesired temperature level is maintained throughout the entire die bodyportion 40, assuring that the polymer melt as well as the core memberare maintained at the desired temperatures in each and every areathereof.

Any known, conventional heating means may be employed in cavities 58,59, 60, and 61 in order to produce and maintain the precisely desiredtemperature levels. Such heating means commonly employed in the industryinclude both electrical and conventional heating means commonly employedin the industry which include water, oil, cartridge heaters, and heaterbands. These heating means or any other conventional heating means canbe employed in die 30, without departing from the scope of thisinvention.

In addition, in order to assure that the desired temperature levels aremaintained throughout cross head extrusion die 30, the preferredembodiment of the present invention incorporates a heating jacket whichperipherally surrounds die 30 and maintains die 30 at the preciselydesired elevated temperature level. In this way, temperaturedifferentials are eliminated and the elevated temperature desired forcore member 21 and the polymer melt flowing through delivery channel 50are maintained throughout die 30.

In order to assure that the polymer melt flowing through deliverychannel 50 is maintained at the desired temperature level to produceflow of the polymer melt through cross head extrusion die 30, as well asonto core member 21 at the desired temperature, thermocouples arepreferably placed in various locations of cross head extrusion die 30.In this regard, it has been found that thermocouples should bepositioned at similar locations in the delivery channel at spacings ofat least 180° in order to assure that the polymer melt throughout die 30is at the desired temperature. Furthermore, in the preferredconstruction, temperature deviation of + or -1° C. is maintained. Inthis way, the desired flow and application characteristics sought forthe polymer melt in forming outer layer 22 are attained.

In the preferred embodiment, cross head extrusion die 30 of the presentinvention incorporates several unique construction features in order toachieve the secure, intimate bonded interengagement of outer layer 22with foam thermoplastic or elastomeric core member 21. One of theseunique construction features incorporated into cross head die 30 is theangular relationship at which all polymer melt metering feed line 55 ispositioned relative to smaller diameter section 36 of passageway 31. Asshown in FIG. 2, polymer melt metering fee line 55 is arcuately disposedrelative to the surface of smaller diameter section 36 at an acuteapproach angle designated "A".

In the preferred construction, approach angle "A" preferably rangesbetween about 30° and 90°. By employing an approach angle falling withinthis range, the polymer melt flowing through metering feed line 55 iscapable of exerting sufficient pressure on core member 22 to achieve thedesired, complete, thorough, bonded interengagement between core member21 and outer layer 22.

Although approach angles ranging between about 30° and 90° have beenfound to produce highly effective results, an optimum approach angle "A"has been found to range between about 60° to 75°.

In addition, in the preferred construction of cross head extrusion die30 of the present invention, smaller diameter section 36 of passageway31 incorporates an outer layer forming zone or land 65 extending betweeninterior portal 52 of metering feed line 55 and exit portal 33 ofpassageway 31. In the preferred embodiment, zone/land 65 comprises awidth ranging between 0 mm and 30 mm. By forming zone/land 65 in thismanner, a forming area is provided for controlling and producing fullycontacted, interengagement and formation of outer layer 22 in secure,affixed, bonded interconnection with core member 21.

Although the width of zone/land 65 preferably ranges between about 0 mmand 30 mm, it has been found that optimum results are attained whereinland 65 has a width ranging between about 0 mm and 5 mm. By employingthis construction, optimum results have been realized.

In addition to producing secure, bonded affixation of outer layer 22 tocore member 21 by employing zone/land 65 with the desired width detailedabove, the diameter of zone or land 65 is constructed to be greater thanthe diameter of smaller diameter section 36 of passageway 31 directlyadjacent interior portal 52. By controlling the diameter of formingzone/land 65, the precisely desired thickness for outer layer 22 iscontrolled and established.

Consequently, if a substantially thin outer layer 22 is desired, thediameter of forming zone/land 65 is slightly greater than the diameterof section 36. However, when a substantially thicker outer layer 22 isbeing formed, zone/land 65 is constructed with a diameter substantiallygreater than the diameter of section 36. In this way, any desiredthickness can be easily accommodated for outer layer 22, while alsoassuring secure, bonded affixation of outer layer 22 to core member 21.

Another structural feature incorporated by cross head extrusion die 30of the present invention is the construction and operation of central orintermediate section 35 of passageway 31. As discussed above,intermediate section 35 comprises a ramped, sloping configurationextending between larger diameter section 34 and smaller diametersection 36. In addition, annular cavity 61 is positioned in juxtaposed,spaced, cooperating relationship with section 35 for providing thedesired elevated temperature to section 35.

In the preferred embodiment, section 35, with heated annular cavity 61cooperatively associated therewith, causes the outer surface of coremember 21 to be heated as core member 21 longitudinally advances throughpassageway 31 in the direction shown by arrow 68. By heating the outersurface of core member 21, the gas(es) trapped within the closed cellsadjacent the outer surface of core member 21 are released as the cellsare ruptured. Once released, the gases are drawn into annular interiorcavity 45 and removed from die 30 through vacuum channel 42.

In addition, as detailed above, intermediate or central section 35 ofpassageway 31 comprises a ramped, sloping configuration whicheffectively squeezes or compresses core member 21 as core member 21advances through extrusion die 30 of the present invention. Bysimultaneously heating the surface of core member 21 while alsocompressing or squeezing member 21 from a larger diameter to a smallerdiameter, the number of cells being broken is optimized and the gasretained therein in released and removed.

As core member 21 emerges from the sloped, ramped intermediate section35 and enters smaller diameter section 36, the outer surface of coremember 21 is brought into contact with the polymer melt forming outerlayer 22. Since the polymer melt is maintained at an elevatedtemperature, above the melting point of the polymer material, theapplication of the hot polymer melt to the surface of core member 21causes any remaining cells to be ruptured as contact is made betweencore member 21 and the hot polymer melt of outer layer 22. Any gasemerging from these ruptured cells passes between central section 35 andcore member 21 to be withdrawn through annular interior cavity 45 andvacuum channel 42.

By employing the construction detailed above for cross head extrusiondie 30, a substantial quantity of the closed cells adjacent the outersurface of core member 21 are ruptured and the gas entrapped therein isremoved prior to the application of outer layer 22. This process hasbeen found to be of particular importance in assuring a secure,intimate, bonded interengagement between outer layer 22 of core member21 as well as in providing a surface on core member 21 which issubstantially enhanced for bonded interengagement with outer layer 22.

In this regard, it has been found that the rupturing of the cells nearthe surface of core member 21 prior to the application of outer layer 22effectively increases the density of the outer surface of core member21. This densification process has been found to be of particularimportance in providing secure, bonded affixation of outer layer 22 tothe outer surface of core member 21.

One beneficial result achieved by rupturing the closed cells near theouter surface of core member 21 is the virtual elimination of anypossibility that the cells will be ruptured after the application ofouter layer 22. By rupturing the cells prior to the application of outerlayer 22 and removing the gas retained therein, the possibility thatpockets of the entrapped gases might be formed between outer layer 22and core member 21 is virtually eliminated.

Another benefit derived from the densification of the outer surface ofcore member 21 is a substantial increase in the peel strength resultingbetween core member 21 and outer layer 22. It is well established thatthe tear strength of a foamed plastic material is directly proportionalto the density of the material. Consequently, the density increaseachieved at the surface of core member 21 causes the tear strength ofthe surface of core member 21 to be proportionally increased.

As a result, once outer layer 22 is securely bonded to core member 21,the effective bonded interengagement between outer layer 22 and coremember 21 is on the outer surface of core member 21, the preciselocation where the density of the core member 21 has been increased. Asa result, due to the increased tear strength resulting from thedensification of the outer surface of core member 21, the effective bondand peel strength between outer layer 22 and core member 21 is similarlyincreased and substantially enhanced.

In this regard, it has been found that by employing the plasticformulation detailed above for core member 21, any desired polymer meltmay be employed for outer layer 22. By incorporating metallocenecatalyzed polyethylene as one of the plastic materials employed informulating core member 21, as detailed above, the resulting member coremember 21 incorporates a uniquely desirable physical attribute. Thephysical attribute produced is a substantial increase in the meltstrength or tack strength of the resulting core member, which causescore member 21 to be securely bonded to any component applied to theouter surface thereof at a temperature sufficient to melt the surface ofcore member 21.

As detailed above, since outer layer 22 is applied to core member 21 ata substantially elevated temperature, the surface of core member 21 iseffectively melted, thereby providing bonded inter-engagement of outerlayer 22 with core member 21 wherein the contacting surfaces areeffectively melted in interengagement with each other. As a result, theresulting integrally bonded, multilayered foam member profile 20produced has outer layer 22 effectively integrally molded or bonded ontocore member 21 wherein removal of outer layer 22 from core member 21requires forces which are incapable of being produced by normal physicalor chemical attacks.

In order to form outer layer 22 on core member 21 using cross headextrusion die 30 of the present invention, core member 21 must passthrough passageway 31 of die 30 in the direction of arrow 68. Thephysical movement of core member 21 through die 30 may be achieved bypulling core member 21 through die 30, pushing core member 21 throughdie 30, or simultaneously pushing and pulling core member 21 through die30. Regardless of which method is employed, substantially similarresults are attained.

In addition, in order to assure the secure, bonded affixation of outerlayer 22 to core member 21, the dimensions of core member 21 must betightly controlled to enable the outer surface of core member 21 tocontact the walls of passageway 31 while also being capable of freesliding movement therethrough. Consequently, in the preferredembodiment, core member 21 is formed with precise dimensional controlbeing maintained over the outer diameter thereof.

Preferably, foamed thermoplastic or elastomeric core member 21 isproduced with a diameter equivalent to the diameter of larger diametersection 34 of passageway 31 with the tolerances of this diameter beingmaintained at +1 mm. By controlling the production of core member 21 topossess a diameter equivalent to the diameter of section 34 ofpassageway 31 or +1 mm greater than this diameter, assurance is providedthat the desired heat transfer from die 30 to core member 21 isattained, while also assuring that the frictional drag between coremember 21 and die 30 can be easily overcome to produce the desired,smooth, continuous production application of outer layer 22 to thesurface of core member 21. Furthermore, if desired, passageway 31 of die30 may be coated with low friction material in order to reducefrictional drag and enhance the movement of core member 21 through die30.

In addition to controlling the diameter of core member 21, the overallroundness or ovality of core member 21 must also be tightly controlled.As a result, guides and sizing apparatus, well known in the art, arepreferably employed to assure that the cross-section of core member 21is circular in each location throughout the length of core member 21,with tolerances being maintained at +/-1.5 mm. It has been found that byproducing core member 21 with these tolerances, the desired heattransfer and frictional contact between core member 21 and extrusion die30 are attained. Furthermore, it has also been found that by providingcore member 21 with dimensions substantially equivalent to the preciselydesired normal dimensions, increased bonded interengagement is realizedbetween outer layer 22 and core member 21.

In view of the fact that tolerances of core member 21 is extremelyimportant to produce intimate bonded interengagement of outer layer 22to core member 21, it has also been found that in any particular productrequiring a substantially thick outer layer 22, such product ispreferably produced by passing the product through a series of extrusiondies in order to build up outer layer 22 to the precisely desiredthickness. Since the positioning and precise axial alignment of coremember 21 with extrusion die 30 is critical in achieving a complete,integral bonded engagement of outer layer 22 to core member 21, theapplication of substantially thick outer layers becomes increasingdifficult. However, by employing multiple passes through a plurality ofextrusion dies, each possessing the dimensions required, the intimate,bonded interengagement of outer layer 22 to core member 21 can beachieved, with outer layer 22 possessing any desired thickness.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained and,since certain changes may be made in carrying out the above method andin the article set forth without departing from the scope of theinvention, it is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween.

Particularly, it is to be understood that in said claims, ingredients orcompounds recited in the singular are intended to include compatiblemixtures of such ingredients wherever the sense permits.

Having described our invention, what we claim as new and desire tosecure by letters patent is:
 1. A foamed multilayer thermoplastic orelastomeric member wherein each of said layers are integrally bonded tothe adjacent layer, said member comprising:A. a core member formed fromextruded foamed plastic materiala. having a density ranging betweenabout 10 kg/m³ and 500 kg/m³, and b. comprising between about 5% and 95%by weight of the entire weight of the core member of at least onemetallocene catalyzed polyethylene; and B. an outer layer peripherallysurrounding and substantially enveloping said core member providing anouter protective surface thereto and having a density ranging betweenabout 100 kg/m³ and 1,200 kg/m³.
 2. The foamed, multilayeredthermoplastic or elastomeric member defined in claim 1, wherein saidouter layer is further defined as being integrally bonded directly tothe surface of the core member for providing a protective outer surfacecapable of withstanding physical and environmental exposures andattacks.
 3. The multilayered foamed thermoplastic or elastomeric memberdefined in claim 1, wherein said core member further contains a plasticmaterial selected from the group consisting of inert polymers,homopolymers, copolymers, and mixtures thereof.
 4. The multilayeredfoamed thermoplastic or elastomeric member defined in claim 3, whereinsaid plastic material is further defined as comprising one or moreselected from the group consisting of high density plastics, low densityplastics, open cell plastics, and closed cell plastics.
 5. Themultilayered foamed thermoplastic or elastomeric member defined in claim3, wherein the plastic material comprises one or more material selectedfrom the group consisting of polyethylenes, polybutylenes,polyurethanes, silicones, vinyl based resins, thermoplastic elastomer,polyesters, ethylene acrylic copolymers, ethylene-vinyl-acetatecopolymers, ethylene-methyl acrylate copolymers, ethylene-butyl-acrylatecopolymers, ethylene-propylene-rubber, styrene buta-diene rubber,ethylene-ethyl-acrylic copolymers, ionomers, polypropylenes, andcopolymers of polypropylene and copolymerizable ethylenicallyunsaturated commoners.
 6. The multilayered foamed thermoplastic orelastomeric member defined in claim 1, wherein said metallocenecatalyzed polyethylene is further defined as comprising one or morepolyethylene selected from the group consisting of high density, mediumdensity, low density, linear low density, ultra high density, and mediumlow density.
 7. The multilayered foamed thermoplastic or elastomericmember defined in claim 1, wherein said metallocene catalyzedpolyethylene is further defined as ranging between about 20% and 60% byweight of the entire weight of the composition of the core member. 8.The multilayered foamed thermoplastic or elastomeric member defined inclaim 7, wherein the density of the core member is further defined asranging between about 10 kg/m³ and 100 kg/m³.
 9. The multilayered foamedthermoplastic or elastomeric member defined in claim 8, wherein the coremember is further defined as having cells having a size ranging betweenabout 0.5 mm and 10 mm.
 10. The multilayered foamed thermoplastic orelastomeric member defined in claim 1, wherein said core member isfurther defined as further comprising one or more additives selectedfrom the group consisting of flame retardants, ultraviolet stabilizers,nucleating agents, physical blowing agents, chemical blowing agents,volume stabilizing agents, colorants, and pigments.
 11. The multilayeredfoamed thermoplastic or elastomeric member defined in claim 1, whereinsaid outer layer is further defined as comprising a thickness rangingbetween about 0.1 mm and 5 mm and comprising a density ranging betweenabout 100 kg/m³ and 500 kg/m³.
 12. The multilayered foamed thermoplasticor elastomeric member defined in claim 1, wherein said outer layer isfurther defined as being formed from plastic material selected from thegroup consisting of metallocene catalyzed low density polyethylenes, lowdensity polyethylenes, ethylenic copolymers, ethylene-vinyl-acetates,ethylene-butyl-acrylates, ethylene-methyl acrylate, ethylene acrylicacids, di-block and tri-block ethylene styrene, and ethylene butylenestyrene copolymers.
 13. The multilayered foamed thermoplastic orelastomeric member defined in claim 12, wherein said outer layer isfurther defined as incorporating one or more additives selected from thegroup consisting of density reducing agents, physical blowing agents,chemical blowing agents, pigments, flame retardants, ultravioletstabilizers, talc, fibers, and fillers.